WO2000060680A1 - Active material of positive plate, nonaqueous electrolyte secondary cell, method for producing active material of positive material - Google Patents

Abstract

An active material of a positive plate containing particles made of a compound the composition of which is expressed by a general formula LixMyPO4 (wherein 0∫x≤2, 0.8≤y≤1.2, and M is an element out of the 3d transition metals) and having a particle size of 10νm or less. The active material can be used for a nonaqueous electrolyte secondary cell, and contributes to achieving an excellent cycle characteristic and a high capacity.

Description

 Technical Field The present invention relates to a positive electrode active material capable of reversibly doping / de-doping lithium, and a method for using the positive electrode active material. The present invention relates to a non-aqueous electrolyte secondary battery, and a method for producing this positive electrode active material. BACKGROUND ART In recent years, along with the dramatic progress of various electronic devices, rechargeable secondary batteries have been studied as batteries that can be used conveniently and economically for a long time. Lead-acid batteries, alkaline batteries, lithium secondary batteries, etc. are known as typical secondary batteries.

 Among the above secondary batteries, lithium secondary batteries have advantages such as high output and high energy density. A lithium secondary battery is composed of a positive electrode having at least an active material capable of reversibly inserting and removing lithium ions, a negative electrode, and a non-aqueous electrolyte.

As the positive electrode active material of this lithium secondary battery, Li i 0 0: i i N i O L i M n ₂構造 having a positive spinel structure and a space group F d 3 m is practically used. However, a positive electrode active material that is more economical, can be supplied stably, and realizes stability, high capacity, and good cycle characteristics is required. Currently, a compound having an olivine structure as a positive electrode active material of a lithium secondary battery, for example, a general formula L i .MPO, (where X is in the range of 0 <X ≤ 2 and y force S 0. In the range of 8≤y≤1.2, M contains a 3d transition metal.) The compound represented by is considered a promising material,

Among the compounds represented by LiM and .P ^, for example, LiFePO is used in a positive electrode of a lithium ion battery, and has been proposed in Japanese Patent Application Laid-Open No. Hei 9-117187.

L i Fe P〇 has a theoretical capacity of as high as 170 mA h / g, and L i can be electrochemically dedoped in the initial state! Since it contains one atom per ⁷ e atom, it is a promising material as a positive electrode active material for lithium ion batteries.

L i F e PO ₄ is conventionally used divalent salts of iron such as iron acetate F e (CH a COO) ₂ as a F e source comprising a synthetic material, 8 0 0 ° under a reducing environment C _c but it has been synthesized by relatively being fired at a high temperature of, in the actual battery constituted by using the L i F e PO synthesized by the synthesis method described above with the positive electrode active material, 6 O mAh Z g ~ 70 mAh / g The actual capacity is only obtained; the above-mentioned publication (reported here); then, Journal o the Electrochemical Society , 144, 1188 (1997) reported an actual capacity of about 120 mAhZg, but considering that the theoretical capacity is 170 mAh / g, a sufficient capacity was considered. I can't say it has.

Further, when the L i F e P_〇 and L i M n ₂ O ■! Compared, and a L i F e PO, the volume density of 3. 6 g Z cm, the average voltage is 3. 4 V der that whereas, L i M n ₂ O ₄ is the volume density of 4. 2 g Z cm ^3, the average voltage is 3. 9 V, has a capacity of 1 2 0 m a h Z g ing Therefore, Li Fe P〇 is about 10% smaller in voltage and volume density than Li M n. Therefore, if the capacity is the same, _{120 mA Ah} / g, L i F e PO is, L i M n O 1% or more by weight energy one density than the 20% or more small and connexion want cormorant _c for the volume energy density, L i F e PO in L i M 11 ₂ In order to achieve an energy density equal to or higher than O, a capacity of 14 O m A hg or more is required, but such high capacity has never been achieved with Li Fe P〇. Had not been realized.

 In addition, LiFe synthesized by baking at a relatively high temperature of 800 ° C. sometimes excessively crystallized and hindered the diffusion of lithium. For this reason, a nonaqueous electrolyte secondary battery could not obtain a sufficiently high capacity. Furthermore, if the temperature at the time of firing is high, energy is consumed correspondingly, and the load applied to the reaction device and the like is also large. DISCLOSURE OF THE INVENTION An object of the present invention is to provide a positive electrode active material that achieves a high capacity when used in a battery, and a nonaqueous electrolyte secondary battery using the positive electrode active material.

In order to achieve the above object, the positive electrode active material according to the present invention has a general formula Li _x MPO (where X force; 0 <X ≤ 2, y force; 0.8 ≤ y ≤ 1 .2 in which M contains a 3d transition metal.) Contains a compound represented by), and L _x M, .P〇 includes those with a particle size of 10 m or less. It is characterized by. The positive electrode active material according to the present invention configured as described above contains Li, {νΡ} having a particle diameter of 10 μm or less. Accordingly, the positive electrode active material has a particle size distribution that allows the charge carrier, for example, lithium to be sufficiently diffused in the positive electrode active material particles. Further, the positive electrode active material according to the present invention has a general formula Li x (F e, M,-,) Ρ (however, the force is in the range of 0.9 ≤ χ ≤ 1.1, the y force is 0 <y ≤ a range of 1, containing a compound M is represented by containing 3 d transition _{metals), L i x (F e} .. · M, -. ;,) POJ is Mossbauer spectroscopy In the spectrum obtained by the method, the area intensity of the spectrum in which the isomer shift value is in the range of 0.1 mm / sec or more and 0.7 mm / sec or less is A, and the isomer shift value is A. A / B is less than 0.3, where B is the area intensity of a spectrum having a range of 0.8 mm / sec or more and 1.5 mm / sec or less. .

 Since the AZB of the positive electrode active material according to the present invention configured as described above is less than 0.3, the presence of electrochemically inactive impurities is small, and high capacity is realized.

Further, the nonaqueous electrolyte secondary battery according to the present invention has a general formula Li _x M.PO (where is 0 <x ≤ 2), which is capable of reversibly doping and undoping lithium. 0.8 ≤ y ≤ 1.2, and M contains a 3d transition metal.) A positive electrode having a positive electrode active material containing a compound represented by the following formula: a negative electrode having a dedoped negative electrode active material, in a non-aqueous electrolyte and the aqueous 1 solution electrolyte secondary batteries having a, L i _x MVPO include those having a particle diameter of not more than 1_ 0 mu m It is characterized by the following.

The non-aqueous electrolyte secondary battery according to the present invention configured as described above has a positive As a polar active material, the particle size is less than 0 / m and contains iMPO. This positive electrode active material has a particle size distribution that allows lithium as a charge carrier to sufficiently diffuse in the particles. Therefore, a non-aqueous electrolyte secondary battery having a high capacity is realized.

In addition, the nonaqueous electrolyte secondary battery according to the present invention has a general formula L (F e, M) P O. (where X force; 0.9 ≤ x ≤ 丄 .1, y force; 0 ≤ y ≤], and M contains a 3d transition metal. Positive electrode and reversible lithium! In a non-aqueous electrolyte secondary battery including a negative electrode having a negative electrode active material capable of removing the Z-dope and a non-aqueous electrolyte, Mixbauer spectroscopy is performed using Li _x (F e M,-,). In the spectrum obtained by the method, the area intensity of the spectrum having an isomer shift value in the range of 0.1 mm / sec or more and 0.7 mn / sec or less is defined as A, A / B is less than 0.3, where B is the area intensity of the vector whose shift value is 0.8 mm / sec or more and 1.5 mm / sec or less. _ΰ

 The non-aqueous electrolyte secondary battery according to the present invention configured as described above contains a positive electrode active material having a value of less than 0.3 and a small amount of i-chemically inert impurities. As a result, a non-aqueous electrolyte secondary battery having a high capacity t is realized.

 Another object of the present invention is to provide a method for producing a positive electrode active material that achieves high capacity when used in a battery.

In order to achieve the above object, a method for producing a positive electrode active material according to the present invention uses a general formula Li _x MPO (where X is in the range of 0 to X 2 and V force S 0.8 ≤>'≤ 1.2 range, M force'; contains 3d transition metal You. A mixing step of mixing the raw materials for synthesis of the compound represented by the formula (1) to form a precursor, and a firing step of firing and reacting the precursor obtained in the mixing step. It is characterized in that the precursor is fired at a temperature in the range of not less than ° and not more than 700 t.

In the method for producing a positive electrode active material according to the present invention configured as described above, in the firing step, the precursor of Li, λ] Ρ〇 is used at a temperature of not less than 400 ° C. and not more than 700. Has been fired. As a result, the chemical reaction and the crystallization proceed uniformly, and the crystallization does not proceed excessively, so that a single-phase Li x MP〇 without impurities can be obtained. The firing step is L i _X M, the temperature difference of firing the precursor of P_〇, L i _chi Micromax, powder characteristics · P changes dramatically. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a configuration example of a nonaqueous electrolyte secondary battery to which the present invention is applied.

 FIG. 2 is a characteristic diagram showing a powder X-ray diffraction pattern of LiFcPO synthesized from samples 1 to 5 of sample.

 FIG. 3 is a characteristic diagram showing the relationship between the sintering temperature of LiFePo synthesized in samples 1 to 5 and the charge / discharge capacity of the battery.

 FIG. 4 is a characteristic diagram showing the relationship between the sintering temperature and the volume particle size distribution of Li FePO synthesized in Samples I to 5.

 FIG. 5 is a characteristic diagram showing the relationship between the sintering temperature and the cumulative volume diameter of Li Fe Ρ サ ン synthesized in sembles 1 to 5.

Fig. 6 shows the results obtained by combining samples 1 to 5 with a particle size of 0.1 u. FIG. 4 is a characteristic diagram showing the relationship between the firing degree of LiFePO in the range of m to l and the cumulative volume diameter.

 Fig. 7 is a scanning micrograph showing the particle shape of Li FeP with a firing temperature of 50 °-Fig. 8 is the particle shape of LiFeP with a firing temperature of 600C Is a scanning micrograph showing

 Figure 9 is a scanning micrograph showing the particle shape of Li FeP〇 at a firing temperature of 700 ° C.

 FIG. 10 is a characteristic diagram showing the {Τ} specific surface area of LiFePo, synthesized in Samples 1 to 5.

 FIG. 11 is a characteristic diagram showing a powder X-ray diffraction pattern of Li FePO synthesized in Samples 1, 5, and 6.

 FIG. 12 is a characteristic diagram showing the charge / discharge characteristics of the battery manufactured in Sample 1.

 FIG. 13 is a characteristic diagram showing the cycle characteristics of a battery manufactured as a sample.

 FIG. 14 is a characteristic diagram showing the charge / discharge characteristics of the battery manufactured in Sample 5.

 FIG. 15 is a characteristic diagram showing the charge / discharge characteristics of the battery manufactured in Sample 6.

1 _{6, L i (M n u.} 6 F eu.,) Is a view to characteristic diagram of the X-ray diffraction butter Ichin of PO.

FIG. 17 is a diagram showing the charge / discharge characteristics of a battery manufactured using Li (nu.6Feu.,) P.- FIG. 18 is obtained by firing at 600 ° C. L i (n ₆ F e _u .,) It is a figure which shows the particle size distribution of P.

Figure 1 9 is a Mesubauasu Bae-vector diagram of a L i F e P_〇 Samburu 6 synthesized by the firing temperature and 3 2 0 C _c

2 0 is a main Sunoku Wasu Bae-vector diagram of a L i F e PO of the firing temperature 4 0 0 ° C and to the synthesized samples 2 _c

 FIG. 21 is a Mesno vector diagram of LiFePo of Samburu synthesized at a firing temperature of 600.

 FIG. 22 is a Mesuno spectrum diagram of Fe— of LiFePo of sample 6.

 FIG. 23 is a Mesuno-vector diagram of Fe of LiFeP〇 of sample 6. FIG.

 FIG. 24 is a Mesno vector diagram of Fe ^ of LiFeP〇 of sample 2.

2 5 is a Mesunoku Wasu-vector diagram of F e ³ of Sample 2 L i F e PO _4.

2 6 is a Mesunoku Wasu-vector diagram of F e ² of the sample 1 of L i F e PO _{4 =}

FIG. 27 is a mesh map of Fe ³ of Li Fe PO ^ of sample 1. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, a nonaqueous electrolyte battery 1 to which the present invention is applied contains a negative electrode 2, a negative electrode can 3 containing the negative electrode 2, a positive electrode 4, and a positive electrode 4. It comprises a positive electrode can 5, a separator 6 disposed between the positive electrode 4 and the negative electrode 2, and an insulating gasket 7. The negative electrode can 3 and the positive electrode can 5 are filled with a non-aqueous electrolyte:

The negative electrode 2 is formed by forming a negative electrode active material layer containing a negative electrode active material on a negative electrode current collector. Is a negative electrode current collector, that need use such as nickel foil is _c

 As the negative electrode active material, a material capable of doping / de-doping lithium is used. Specifically, metallic lithium, a lithium alloy, a conductive polymer doped with lithium, a layered compound (carbon Materials and gold oxides).

 As the binder contained in the negative electrode active material layer, a known resin material or the like which is generally used as a binder for the negative electrode active material layer of this type of nonaqueous electrolyte battery can be used.

 Further, as the negative electrode 2, for example, a metal lithium foil serving as a negative electrode active material may be used.

 The negative electrode can 3 houses the negative electrode 2 and serves as an external negative electrode of the nonaqueous electrolyte battery 1.

 The positive electrode 4 is formed by forming a positive electrode active material layer containing a positive electrode active material on a positive electrode current collector.

Although the production method of the positive electrode active material will be described later, it has an olivine structure, and has a general formula of L _x M, .PO (where X force) and X ≤ 2 and y force S 0 8≤y≤1.2, where M contains a 3d transition metal. ) Is used.

Compounds represented by Li _x M v P include, for example, Li Fe PO ■ !, Li _x M n POL i _x Co PO, Li _x N i, PO and i . C uv PO 4 L i. (F e, M n) ■ POL i x (F e, C o), POL i (F e, N i), L i s (C u, M n) to PO PO ;, L i (C u, C o), PO to L i, (C u, N i). PO, L

(M n, T i), to PO L (n, Z n), P〇 ■ ;, L i (M n, g), 〇4, etc. (The composition ratio in () is arbitrary :. ).

Here, i M and PO include those having a particle diameter of .10 μm or less ₌ L i M and PO contained in the positive electrode active material, and L i having a particle diameter of 10 μm or less. ₍ 4) When PO 4 is not contained, lithium as the charge carrier cannot be sufficiently diffused in the particles of the positive electrode active material because the particle size distribution is not appropriate.

Further, when L _x M> P〇4, the 10% volume cumulative diameter is preferably 1 m or less. If the 10% volume cumulative diameter is larger than 1 μm, Li _X M and .PO have a large amount of giant particles due to excessive crystallization. For this reason, there is a concern that lithium, which is the I carrier, cannot be diffused smoothly in the particles of the positive electrode active material.L i 〇4 has a Brunauer-Emmett's tailor (BET) specific surface area. 0.5 m ² Zg or more is preferable: In the case of a positive electrode active material having a large particle diameter, the surface area is reduced. In such a situation, when a large current is passed, that is, a large amount of lithium ion is used in a short time. When lithium is introduced into the active material, the diffusion of lithium in the active material cannot catch up with the supply of lithium from the outside, and the capacity apparently decreases: Therefore, in order to secure sufficient capacity even under a large current Is to increase the specific surface area and, as mentioned above, to reduce the particle size. Measures are needed-

By setting the BET specific surface area of Li _x M., PO to 0.5 m ^; / g or more, diffusion of lithium in the active material is accelerated, and sufficient capacity can be secured even under a large current.

Further, in the compound represented by the general formula L i _Χ Μ P〇, a compound in which Μ contains Fe as a 3 d transition metal, that is, (F e Μ) Ρ Ο (where Ρ Force; 0.9 ≤ ≤ ≤ 1.1, y force; 0 < _y ≤ l, and M contains a 3d transition metal.) In the spectrum obtained by Mossbauer spectroscopy, the area intensity of a vector whose isomer shift value is in the range of 0.1 mm Z sec or more and 0.7 mn / sec or less is A, Body shift, ◦ .8 mm Z sec or more, 1.5 mm / sec or less ii ': When the area intensity of the spectrum enclosed by Li is B, A / B is less than 0.3. Use something.

For example, in L i (F e M,) P〇, L i F e P〇 which is x force; 1 and y force S 0 is, according to Mesbauer spectrometry, a Mesbauer ぺ equivalent to F e. As a vector, a doublet having an isomer shift value of about 1.2 mm / sec and a quadrupole splitting of about 2.9 mm / sec is observed. Also, if F e is oxidized F e are present in the L i F e Ρ Ο · » , as the F e ³ Ί this corresponding menu Subauasu Bae click Bok Le, isomers shift value 0. Doublet in the range of 1 mm / sec or more and 0.7 mm / sec or less is observed

L i F e P_〇 and simultaneously L i escapes in the course of the initial charge. F e ^{2 ÷} is F e ³ Ί this oxidation. If is contained in Li Fe ₄ 04 before the initial charge, the number of electrons contributing to the battery reaction decreases. As a result, the charge capacity of the lithium ion secondary battery is reduced as a result.

Since the lithium ion secondary battery uses a material that does not contain Li, such as carbon, for the negative electrode, the initial charge capacity determines the subsequent battery capacity. Further, the lithium ion secondary battery, even when using a material containing L i in the negative electrode, the phase containing F c ³ 'is electrochemically inactive, the presence of the inert phase There is a possibility that the battery capacity is reduced. For this reason, it is preferable that the amount of Fe ³ present in LiFePO be as small as possible before the initial charging.

The area intensity A is proportional to the presence ft of Fe present in LiFeP, and the area intensity B is proportional to the amount of Fe present in LiFePO. Accordingly, A / B is 0. Less than 3 L i F e PO has less abundance of F e ^{3 +,} a non-aqueous electrolyte secondary you containing the L i F e P as a positive electrode active material High capacity batteries are realized.

It is a positive electrode current collector, for example, as a secondary aluminum © binders beam foil is contained in the _c positive electrode active material layer used, the binding of the positive active material layer of nonaqueous electrolyte batteries of this type As the agent, a known resin material or the like generally used can be used.

 The positive electrode can 5 accommodates the positive electrode 4 and serves as an external positive electrode of the nonaqueous electrolyte battery 1.

The separator 6 separates the positive electrode 4 and the negative electrode 2 from each other, and can use a known material that is generally used as a separator of this type of nonaqueous electrolyte battery. For example, a polymer film such as polypropylene is used. The thickness of the separator should be as small as possible due to the relationship between lithium ion conductivity and energy density. It is. Specifically, the thickness of the separator is preferably, for example, 50 m or less.

 The insulating gasket 7 is incorporated into and integrated with the negative electrode can 3. The insulating gasket 7 is for preventing the leakage of the nonaqueous electrolyte filled in the negative electrode can 3 and the positive electrode can 5. -As the non-aqueous electrolyte, use a solution in which an electrolyte is dissolved in a non-protonic non-aqueous solvent.

 Non-aqueous solvents include, for example, propylene carbonate, ethylene-carbonate, butylene carbonate, vinylene-force, γ-butynolactone, sulfolane, 1,2-dimethoxetane, 1,2-diethoxyxetane , 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, methyl propionate, methyl butyrate, dimethyl alcohol, getylcabonate, lipstick hillcarbonate, etc. it can. In particular, from the viewpoint of voltage stability, annular force such as pyrene carbonate, vinylene carbonate, and the like, dimethinocarbonate, jetinore carbonate, jib mouth pillcarbonate, etc. It is preferable to use chain carbonates such as In addition, such a non-aqueous solvent may be used alone or as a mixture of two or more.

Further, as the electrolyte to be dissolved in the nonaqueous solvent, for _{example, L i PF 6, L i} C 1 OL i A s F 6, L i BF, L i CF 3 SO 3, L i N (CF a SO ,) And the like can be used. Among these lithium salts, it is preferable to use Li PFπ and Li BF.

Non-aqueous electrolyte battery using ix MPO as positive electrode active material 1 is produced, for example, as follows.

As the negative electrode 2, first, a negative electrode active material and a binder are dispersed in a solvent to prepare a negative electrode mixture of a slurry. Next, the obtained negative electrode mixture is uniformly applied on a current collector and dried to form a negative electrode active material layer, whereby negative electrode 2 is produced. As the binder for the negative electrode mixture, a known binder can be used, and a known additive or the like can be added to the negative electrode mixture. Further, metallic lithium as the negative electrode active material can be used as it is as negative electrode _2c

As the positive electrode 4, first, Li _x M ... PO as a positive electrode active material and a binder are dispersed in a solvent to prepare a slurry positive electrode mixture. The positive electrode 4 is produced by uniformly applying the positive electrode mixture on the current collector and drying to form a positive electrode active material layer. As the binder of the positive electrode mixture, a known binder can be used, and a known additive or the like can be added to the positive electrode mixture.

 A non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent.

 Then, the negative electrode 2 is accommodated in the negative electrode can 3, the positive electrode 4 is accommodated in the positive electrode can 5, and a separator 6 made of a porous film made of polypropylene is disposed between the negative electrode 2 and the positive electrode 4. . A non-aqueous electrolyte is poured into the negative electrode can 3 and the positive electrode can 5, and the negative electrode can 3 and the positive electrode can 5 are caulked and fixed via the insulating gasket 7, thereby completing the non-aqueous electrolyte battery 1. .

By the way, in the method for producing a positive electrode active material to which the present invention is applied, the positive electrode active material has an olivine structure, and has a general formula L i _X M, -P (X force; 0.9 ≤ X ≤ 1.1). Yes, y force; 0 <y ≤ 1 and contains M force 3 d transition gold bending.) The compound represented by, for example, Li Fe P〇 is shown below. Combine as before.

 First, as a raw material for synthesis, for example, iron acetate (Fe (CH, COO)), ammonium hydrogen phosphate (NimPOj), and lithium carbonate (Li, CO) are mixed at a predetermined ratio to form a precursor. Here, the raw materials for synthesis are sufficiently mixed In order to mix the raw materials for synthesis sufficiently, the raw materials are uniformly mixed and the number of contact points is increased, so that the L i F is lower than before. e PO ■ · can be synthesized.

 Next, the precursor is calcined at a predetermined temperature in an atmosphere of an inert gas such as nitrogen to synthesize LiFeP〇.

 Conventionally, LiFe has been fired at a relatively high temperature of 800 ° C., for example. When the temperature during firing was high, energy was consumed correspondingly, and the load on the reactor and the like was large.

Therefore, the raw materials for synthesis are sufficiently mixed to form a precursor, and the precursor is calcined in a nitrogen stream, so that L is obtained at a temperature of, for example, 300 ° C, which is much lower than the conventional temperature of 8 ° C. It has become possible to synthesize i FeP〇. In other words, it has become possible to synthesize LiFeP〇 ■ · over a wider temperature range than in the past, and the range of selection of the precursor firing temperature (hereinafter referred to as firing temperature) has been broadened. The present inventor has a firing temperature for firing the precursor, L i F e P_〇 focused on relationship between the capacitance of the battery using as an active material, sintering of the optimal L i F e P 0 ₄ As a result of examining the temperature, the firing temperature of LiFePO is specifically set in a range of 400 ° C. or more and 700 ° C. or less. The firing temperature of LiFePO is preferably in the range of 400 ° C. or more and 600 ° C. or less.

If the sintering temperature of LiFePO is lower than 400 ° C, a trivalent iron compound or the like as an impurity, that is, a phase containing Fe exists, and a uniform LiFe If PO cannot be _obtained. Also, if the firing temperature of _LiFeO is higher than ₇₀₀ , crystallization proceeds excessively, and the _{precipitation of} impurities may not be suppressed.

 In the above-described method for producing a positive electrode active material, it is preferable to remove air contained in the precursor by subjecting the precursor to a deaeration treatment before firing the precursor.

If air remains in the precursor, F e ^ in iron acetate, which is a divalent iron compound, is oxidized by oxygen in the air when Li Fe P〇 is calcined. It becomes F e ³ . As a result, an impurity of 3ΙιΙΙί iron compound is mixed into the product LiFePO. By removing the air contained in the precursor by deairing, the iron acetate

Oxidation of F e ² can be prevented. As a result, a single-phase LiFePO can be obtained without the trivalent iron compound being mixed into the product LiFe e.

Also, L i is the F e P 0 ₄ starting materials for synthesis, in addition to compounds described above, lithium hydroxide, lithium nitrate, lithium acetate,-phosphate lithium, ferrous-phosphate, cuprous oxide Although various raw materials such as iron can be used, in order to perform firing at a relatively low temperature of 400 ° C. or more and 700 ° C. or less, it is preferable to use a highly reactive raw material.

Non-aqueous electrolyte secondary battery 1 which is manufactured as described above contain i _x M _y P_〇 to as the positive electrode active substance.

Since this positive electrode active material contains L _x M and P〇 having a particle size of not more than] ΟμΟ, it has a particle size distribution suitable for sufficiently diffusing lithium as a charge carrier. Therefore, as the non-aqueous electrolyte secondary battery 1, lithium doping / de-doping is performed favorably, so that it is excellent. With excellent cycle characteristics and high capacity

In addition, since the positive electrode active material contains Li _x M and P〇 having a 10% volume cumulative diameter of 1 μm or less, diffusion of lithium as a charge carrier occurs more smoothly. Therefore, the non-aqueous electrolyte secondary battery has a better cycle characteristic because the lithium doping / de-doughing is performed better. And high capacity.

 In the method for producing a positive electrode active material as described above, as a compound represented by the general formula Li MPO, for example, a raw material obtained by mixing a synthesis raw material of LiFePO is used as a precursor. Since calcination is performed at a temperature in the range of 0 ° C. or more and 700 ° C. or less, chemical reaction and crystallization proceed uniformly, and crystallization does not excessively proceed. As a result, as the positive electrode active material, a single-phase LiFePo is obtained without any impurities. Therefore, this positive electrode active material can realize a high capacity exceeding the 12 OmAh / g of the conventional nonaqueous electrolyte secondary battery.

Also, L i F _e P_〇 &> sintering temperature 4 0 0 ° C or more, Ri by the fact that the 6 0 0 ° C or less in the range, L i F e PO theoretical a capacitance 1 7 0 m A High real capacity approaching h / g can be realized.

Incidentally, the positive electrode active material according to the present invention is not limited to the above-mentioned L i F e PO, also applies to the compounds represented by the general formula L i M _y PO. Further, the configuration of the non-aqueous electrolyte secondary battery according to the present invention is not limited to the configuration described above, and a solid electrolyte or a gel solid electrolyte containing a swelling solvent may be used as the non-aqueous electrolyte. The shape of the non-aqueous electrolyte secondary battery according to the present invention is not particularly limited, such as cylindrical, square, coin, and button types. 8 Also, various sizes such as thin and large: can be rubbed:

Also, in the method for producing the positive electrode active material, a method based on a solid phase reaction in which powder of a compound as a raw material for synthesis of LiFeP〇; is mixed and fired has been described as an example. is not limited to, can be synthesized general formula L i, 1 P 0 ₄ represented by compound by applying the solid-phase reaction or a solid-phase reaction various chemical synthesis methods other than.

 Hereinafter, specific examples and comparative examples to which the present invention is applied will be described based on experimental results.

Experiment 1〉

 In Experiment 1, a compound represented by the general formula L i χ,, .Ρ Ο 作 製 was prepared as a positive electrode active material, and a nonaqueous electrolyte secondary battery using this positive electrode active material was prepared as a test cell. Then, various characteristics were evaluated.

 First, in order to evaluate the difference in the characteristics of the nonaqueous electrolyte secondary battery due to the difference in the particle size distribution of the positive electrode active material, the sintering temperature was changed to synthesize the positive electrode active material. Next, a test cell was fabricated using this.

 Sample 1

 First, LiFe e as a positive electrode active material was synthesized at a firing temperature of 600 °.

To synthesize LiFeP〇, first, ammonium dihydrogen phosphate (ΝI-ΝII, ΡΡ,) as a raw material having a large crystallite size was sufficiently pulverized in advance. Next, the molar ratio of iron acetate (F e (CHCOO),...), Ammonium dihydrogen phosphate (NI and H ₂ PO), and lithium carbonate (LC〇) was changed to 2: 2: 1. made in sufficient mixed to the precursor _c Next, under a nitrogen atmosphere, after one row calcining of 1 2 more hours at precursor 3 0 0 ° C, under a nitrogen atmosphere, precursor 6 0 Bake at 0 ° C for 24 hours _C obtained by combining the L i F e P_〇 by

 Then, a battery was prepared using Li FePO 4 obtained as described above as a positive electrode active material:

 First, 70% by weight of dried iFePO as a positive electrode active material, 25% by weight of acetylene black as a conductive agent, and 5% by weight of vinylidene fluoride as a binder % Was uniformly mixed with dimethylformamide as a solvent to prepare a paste-like positive electrode mixture. The polyvinylidene fluoride used was # 130 from Aldrich.

 Next, this positive electrode mixture was applied on an aluminum mesh serving as a current collector, and dried at 10 ° C. for 1 hour under a dry argon atmosphere to form a positive electrode active material layer.

 Then, the aluminum mesh on which the positive electrode active material layer was formed was punched into a disk having a diameter of 15 mm to form a pellet-shaped positive electrode. One positive electrode carries 60 mg of an active material. Next, a lithium metal foil was punched into the same shape as the positive electrode to form a negative electrode.

Next, the isochoric amount mixed solvent of pro Pirenkabone one preparative and dimethyl force one Bone bets, to prepare a more nonaqueous electrolytic solution L i PF ₆ to be dissolved at a concentration of I mol /].

 The positive electrode obtained as described above was accommodated in a positive electrode can, the negative electrode was accommodated in a negative electrode can, and a separator was disposed between the positive electrode and the negative electrode. A non-aqueous electrolyte solution was injected into the positive and negative electrode cans, and the positive and negative electrode cans were caulked and fixed, whereby a coin-type 250-inch test cell was manufactured.

Sample 2 A positive electrode active material was synthesized in the same manner as in Sample 1, except that the firing temperature was set at 400 ° C, and a test cell was prepared using this positive electrode active material.

 A positive electrode active material was synthesized in the same manner as in Sample 1, except that the firing temperature was set to 500 ° C., and a test cell was prepared using this positive electrode active material.

 A positive electrode active material was synthesized in the same manner as in Sample 1 except that the firing temperature was set at 700 ° C., and a test cell was prepared using this positive electrode active material.

 Sampnolle 5

A positive electrode active material was synthesized in the same manner as in Sample 1 except that the firing temperature was 800 ° C, and a test cell was prepared using this positive electrode active material. For the positive electrode active material Li Fe ₄ , the powder X-ray diffraction pattern was measured. The measurement conditions of powder X-ray diffraction are shown below.

 Equipment used: Rigaku RINT 250

 X-ray: CuK tt, 40 kV, 100 mA

 Goniometer: Vertical standard, radius 18.5 mm

 Counter monochromator: Used

 Filter: Not used

 Slit width:

Divergent slit (DS) = 1. Receiving slit (RS) = 1 °

 Skuttering slit (S S) = 0.1 o mm

 Counting device: Scintillation counter

 Measurement method: Reflection method, continuous scan

 Scan range: 2 G = 10 to 80

Scan speed de: 4 ^c Z min

Powder X Sen叵1 folding pattern of Samburu. 1 to L i synthesized in samples 5 F e PO ₄ shown in FIG. From Fig. 2, in Li FeP e synthesized in Samples 1 to 5, the presence of impurities other than LiFeP e in the product was not confirmed. The ability to obtain F e PO S

Next, charge / discharge tests were performed on the test cells fabricated in Samples 1 to 5. First, constant current charging was performed on each test cell, and when the battery voltage reached 4.5 V, switching from constant current charging to constant voltage charging was performed, and the voltage was maintained at 4.5 V. The battery was charged as it was. The charging was terminated when the current became less than 0.01 mA / c. Thereafter, discharging was performed, and the discharging was terminated when the battery voltage dropped to 2.0 V. Both charging and discharging were performed at room temperature (23 ° C), and the current density at this time was 0.12 mA / cm ² .

As a result of the charge / discharge test, Fig. 3 shows the relationship between the firing temperature of LiFePO4 synthesized in Samples 1 to 5 and the charge / discharge capacity of the battery. Than 3, the nonaqueous electrolyte secondary battery, the L i F e PO ₄ as a positive electrode active material 4 0 0 ° C or higher, by firing in the range of 7 0 0 ° C or less, and a high capacity It turned out to be something. In the case of a nonaqueous electrolyte secondary battery, the firing temperature of the precursor is not less than 400 ° C and not more than 600 ° C. It was found that the sample had a very high capacity. ₌ Next, the volumetric particle size distribution of the cathode active materials synthesized in Samples 1 to 5 was measured. As a device for measuring the volume particle size distribution, a microphone mouth track particle size analyzer LA-920 (manufactured by Horiba Ltd.) was used. The measurement results of the volume particle size distribution obtained by measuring the scattering of the laser beam using this measuring device are shown in Fig. 4.- As can be seen from Fig. 4, the firing temperature was 600 ° C. If it is larger, the volume distribution of Li FeP with a particle size larger than 10 m increases while shifting the center of the distribution to the large particle side. In addition, the volume distribution of Li FPO with a particle size of 10 m or less is remarkably reduced, while when the firing temperature is 600 ° C or less, the particle size is 10 μm. volume distribution of at which L i F e Ρ Ο below, _c are increased while shifting the center of the distribution to smaller particles

From the results of the volume particle size distribution shown in Fig. 4 and the result of the relationship between the firing temperature and the charge / discharge capacity of the battery shown in Fig. 3, it is concluded that Li It was found to be PO ₄ particles.

 Thus, the nonaqueous electrolyte secondary battery has a very high capacity by containing LiFeP〇 with a particle size of 10 μm or less as the positive electrode active material. I'm sorry.

Here, from the results of the volume particle size distribution measurement, FIG. 5 shows the relationship between the firing temperature of LiFePO and the volume cumulative diameter. From FIG. 5, it can be seen that there is a clear correlation between the question of the particle size of LiFePO and the firing temperature of LiFePO. Therefore, in FIG. 5, those in which the range in particle diameter of 0. 1 ~] 0 μ m , c shown in FIG. 6

As can be seen from Fig. 6, the sintering temperature of LiFePO was 600 ° C or less. In the case of, it is understood that Li F c PO having a particle diameter of 1 μm or less accounts for 10% or more. On the other hand, when the firing temperature of LiFePO is higher than 60 ° C, the LiFePO having a particle size of LiFePO of less than] / im is less than 10%. ₌

The results of the relationship between the firing temperature of LiFePO shown in Fig. 6 and the cumulative volume diameter (particle size in the range of 0.1 to 10 m), and the firing temperature and the charge / discharge capacity of the battery shown in Fig. 3 From the results of the relationship, it is preferable that the non-aqueous electrolyte secondary battery contains, as a positive electrode active material, Li Fe PO ■> having a 10% volume cumulative diameter of 1 μm or less. the, L i F e PO _c which can become to have a high real capacity approaching to the theoretical capacity was divide

Scanning microscope observations were performed on the positive electrode active materials of Sample 3, Sample 1, and Sample 4 in which the firing temperature of LiFeP was 500 O :, 600 ° C, and 700 ° C. went. Figures 7, 8, and 9 show the scanning micrographs of each. These Figures 7, 8, as can be seen from Figure 9, L i F e P 0 4 is specifically grow with increasing calcination temperature, it is clear that the macroparticles. This corresponds well with the result of the volume particle size distribution shown in Fig. 5. From this, it was found that crystallization of LiFePO4 progressed as the firing temperature increased.

 The BET specific surface area of Li FePO synthesized in Samples 1 to 5 was measured. Figure 10 shows the measurement results of the specific surface area. In addition, in FIG. 10, in addition to Samples 1 to 5, measurement was also performed on LiFePO with the firing temperature changed more finely, and the results are also shown.

As can be seen from Fig. 10, the BET specific surface area monotonically changes as the sintering temperature of LiFePO increases, and the range of change is from ²⁰ m2Zg or more. It turns out to be very large, up to 0.5 mg or less:

Then, Figure 1. a 0, L i F e When PO comparing firing temperature and 3 showing the relationship between discharge capacity, L i F BET specific surface area of _e P_〇 is 0 as a cathode active material. 5 m ² / g or more, more preferably at least ^{2 m 2 Z g, L i} F e this and force Tsu force has a high real capacity approaching to the theoretical capacity of the PO, Ru ₌

 Next, in order to study the optimal firing temperature of the positive electrode active material, a positive electrode active material was synthesized at a lower firing temperature than before, and a test cell was prepared as sample 6 using this.

 Sample 6

Except that the firing temperature and 3 2 0 ¾, the procedure of sample 1 was synthesized L i F e PO, the L i F e P 0 ₄ obtained using as a cathode active material, Tess Toseru Made

 First, the powder X-ray diffraction pattern was measured for the positive electrode active material synthesized in Sample 6 and the positive electrode active material LiFeP〇 synthesized in Samples 1 and 5. Figure 11 shows the measurement results. According to Fig. 11, the presence of impurities other than LiFeP〇 in the product of LiFePO synthesized in samples 1, 5, and 6 was not confirmed. It can be seen that e PO has been obtained.

 Next, charge / discharge tests were performed on the test cells fabricated in Samples 1, 5, and 6.

Figure 12 shows the charge and discharge characteristics of the sample 1 battery. According to Fig. 12, the battery of Sample 1 in which the precursor was fired at 600 ° C and iFePO was used as the positive electrode active material had a flat potential around 3.4 V. You can see that there is. In addition, this battery has a reversible charge of 63 mAh / g. Discharge capacity is generated: This value of 163 mAh / g is close to the theoretical capacity of LiFePO, which is 170 mAhZg.

 Cycle times and charge / discharge for sample 1 battery! ! Figure 1.3 shows the relationship with the capacity. From Fig. 13, it can be seen from Fig. 13 that the cycle deterioration of the charge / discharge capacity is extremely small at 1% / cycle, and that stable battery characteristics are obtained.

 On the other hand, in the battery of Sample 5, as shown in FIG. 14, the obtained charge / discharge capacity is very small. This is because the sintering temperature of LiFePO is as high as 800 ° C, so that crystallization proceeds excessively, and lithium does not diffuse sufficiently in the LiFePO particles. Probably because of.

 In addition, as shown in Fig. 15, the battery of sample 6 does not have sufficient charge / discharge capacity. This is presumably because when the firing temperature is as low as 320 ° C., a trivalent iron compound or the like as an impurity, that is, a phase containing Fe ^ is present in LiFePO.

 From the above results, it was found that LiFeP〇 as a positive electrode active material can achieve high capacity when the firing temperature is in the range of 400 or more and 700 ° 0 or less. .

 By firing LiFeP〇 in the range of 400 ° C or more and 600 ° C or less, the 120 mAh / g of the conventional nonaqueous electrolyte secondary battery can be increased. It was found that a high actual capacity was realized.

Et al is added M n C_〇 ₃ to starting material was prepared was i (n F e) Ρ Ο firing by the same method. Fig.1 6 obtained _{L i (M n F e u} .) PO ■ < of an X-ray diffraction diagram "1 6 forceゝal, L i (M n F e 0.,) P is an impurity And a single-phase olivine structure You can see how it works.

Also, 6 0 0 ^{C C} in the firing-obtained _{L i (M n · e F} e u -..,) To 1 7 charge and discharge characteristics of a battery fabricated in the same manner by using a PO Fig. 17 Not only a high capacity of about 50 mA Ah / g was obtained, but also a capacity near 4 V was newly observed, thereby improving the energy density. Can be done.

FIG. 18 shows the results of measuring the particle size distribution of Li (nF e) PO obtained by firing at 600 ° C. Figures 1 8, L i (M n F e u,) PO include those particle size of less than 1 0 mu m, it is seen that contained in the range 1 0% volume cumulative Seki径be 1 m

<Experiment 2>

In Experiment 2, among the positive electrode active materials prepared in Experiment 1 described above, Sample 6 containing Fe for which the Mossbaer effect was observed and having a firing temperature of 320 ° C, and a firing temperature of 400 ° C is C Samburu 2, with respect to the firing temperature is 6 0 0 ° C sample Works i F e PO, was measured Mössbauer spectrum with main Subaua spectroscopy _c

When measuring the Mossbauer vector, Li Fe PO was used as a sample in a hole of a lead plate having a thickness of 0.5 mm and a hole having a diameter of 15 mm. mg justified, the both sides of the hole portion to which was sealed with tape and shines irradiation to ⁵ C o of 1. 8 5 GB q as a γ-ray.

Figure 19 shows the LiF PO PO, spectrum measurement results of Sample 6 obtained by Mossbauer spectroscopy, and Figure 20 shows the LiFe PO spectrum measurement results of Sample 2 Figure 21 shows the spectrum measurement results of LiFePO in [1]. Further, in FIG. 2 2 L i F e P_〇 Huy ₄ of Mesubauasu Bae-vector Tsu Sorted allowed F e ^{2 +} a scan base-vector obtained by the sample 6 shown in FIG. 1 9, the F e spectrum the torque shown in FIG. 2 3 - further, FIG. 4 F e ^{2 +} a bitch torr obtained by Huy tool preparative L i F e P_〇 ₄ Mesubauasu Bae-vector of the sample 2 shown in FIG. 2 0 In addition, the ³ 3+ vector is shown in Figure 25:

Furthermore, in FIG. 2 6 F e ^{2 +} a bitch Torr obtained by Huy tool preparative Mossbauer bitch torr L i F e P_〇 _fourth sample 1 shown in FIG. 2 1, F ^{e; +} the spectrum _c indicating the torque in Fig 7

As shown in Figs. 22, 24 and 26, the original spectrum of LiFePC has an isomer shift corresponding to Fe2 ⁺ of about :! Doublet with 2 mmZ sec and quadrupole splitting of about 2.9 mmZ sec.

In contrast, L i F e P_〇 ₄ samples 6 firing temperature is 3 2 0 ⁼ C, as shown in FIG. 2 3, F isomer shift equivalent to e is about 0. 4 mm / sec and a quadruple split of about 0.8 mm / sec with a broad doublet _c

Here, the area intensity of the doublet corresponding to F e ^: '+, that is, the area intensity of the spectrum whose direct isomer shift is within the range of 0.1 mmZsec or more and 0.7 mmZsec or less is calculated as Let A be the area intensity of the doublet corresponding to Fe ^{2 +} , that is, the area intensity of the spectrum whose isomer shift value is in the range of 0.8 mmZ sec or more and 1.5 mm / sec or less. Table B shows AZB when B is used.

(Hereinafter the margin) Firing temperature A / B

 3 2 0 X: Samburu 6 0.7

4 0 0 ^C C Sample 2 0.3 4

In 6 0 0 ^C C Sanbunore 1 0.1 5 Experiment 1, sample 1, when having conducted the X-ray diffraction with respect to 2 and 6, as shown in FIG. 2, the phase containing the F e ^{3 +,} for example 3 No spectra were detected for the iron compounds with the valencies: However, Moessbauer spectroscopy on samples 1, 2 and 6 as described above confirmed the presence of a phase containing Fe3 ^+. Was. This is because X-ray diffraction only occurs due to long-range interference of crystals, whereas Mossbauer spectroscopy directly detects information near the nucleus:

From Table 1, it was found that Sample 6, which had a low firing temperature of 320 ⁼ C, had relatively many phases containing Fe ^: that did not have long-range order:

From Table 1, A / B is Ri Contact depending on the firing temperature of the L i F e PO _4, as the firing temperature is low, L i F e P_〇 is contained in ₄ F ^e: it is often I understood.

Here, the AZB shown in Table 1, comparing FIG. 3 shows the relationship between L i F e P_〇 baking temperature and the discharge capacity of _4, as AZB is small, i.e., L i F e P 0 It was found that the smaller the amount of the trivalent iron compound containing F e ^{+ in} ₄ , the higher the capacity of the lithium ion secondary battery. Also, L i F e P 0 _4, when the sintering temperature is synthesized as a 4 0 0 ° C or higher AZ B is less than 0.3, it was found to realize a high capacity: Therefore, the lithium ion secondary battery, the use of L i F e P_〇 ₄ AZB is 0.3 as a cathode active material As a result, the positive electrode active material according to the present invention has the general formula Li _x M _: , P〇 ₄ (where X force is in the range of 0 <X ≤ 2, y force is in the range of 0.8 ≤ y ≤ 1.2, and M contains a 3d transition metal.) _{contain, L i x M:, P0} 4 include those having a particle diameter of not more than 1 0 mu m, there is a further BET specific surface area of 0. 5 m ² / g or more - Thus, the The positive electrode active material realizes excellent cycle characteristics and high capacity when used in a non-aqueous electrolyte secondary battery.- Further, the positive electrode active material according to the present invention has a general formula Li _x (F e, M,- ,) Ρ 0 ₄ (except χ is in the range of 0.9 ≤ χ ≤ 1.1, y force is in the range of 0 <y ≤ 1, and M contains the compound represented by 3) _{i x (F e:, M} :,) P 0 4 , the ratio of B to the area intensity a of the scan base-vector obtained Ri by the Mossbauer spectroscopy, AZB is less than 0.3. As a result, when this positive electrode active material is used for a nonaqueous electrolyte secondary battery, an excellent high capacity is realized.

Further, in the nonaqueous electrolyte secondary battery according to the present invention, the L i F e P 0 ₄ obtained by defining the firing temperature and the particle shape by using as the cathode active material has a large capacity The AZB of the non-aqueous electrolyte secondary battery according to the present invention is not more than 0.3. The L i F e P 0 _4, which is the full by using as a cathode active material, the one having a large capacity.

Further, in the method for producing a positive electrode active material according to the present invention, a single-phase L i _X M: .. PC ^ can be obtained without impurities, so that 120 mA Ah It is possible to achieve high capacities in excess of / g:

Claims

3) Claims

1. General formula L i _x M :. PO (where X is in the range of 0 to X2, y force S is in the range of 0.8 ≤ y ≤ 1.2, and M contains 3d transition metal ) Containing a compound represented by the formula:

Above positive electrode active material i _x MPO (± particle diameter and wherein it to contain not more than 1 0 am.

2. The positive electrode active material according to claim 1, wherein the Li i _{Χ and} Μ ₄ have a 10% volume cumulative diameter of not more than] μπι.

3. The positive electrode active material according to claim 1, wherein iM and PO have a Brunauer's composition's Taylor's specific surface area of 0.5 m ² / g or more. .

4. the L ί _x M _y PO _4, the positive electrode active material ranging first claim of claim, which is a L i F e PO.

5. Set L i _x (F e _y M, _-y ) PO (where x force '; 0.9 ≤ x ≤ 1.1, y force; 0 x y 1; M-force; contains 3d transition metal.)

The _{L i x (F ev M,} -) P_〇, in scan Bae-vector Ritokura is by the main Subaua spectroscopy, isomer shift value force; 0. 1 mm / sec or more on, 0.7 A is the area intensity of the spectrum within the range of mm / sec or less, and A is the area intensity of the spectrum whose isomer shift value is within the range of 0.8 mmsec or more and 1.5 mmZscc or less. A positive electrode active material, wherein B / A is less than 0.3.

6. The positive electrode active material according to claim 5, wherein L i (F e Μ,-) is L i Fe PO.

7. General formula Li _x M which can reversibly dope / dedope lithium

P O (where X force is in the range of 0 <X ≤ 2 and y is 0.8 ≤ y ≤ 1.

2, where M contains a 3d transition metal. ), A negative electrode having a negative electrode active material capable of reversibly doping / de-doping lithium, and a non-aqueous electrolyte comprising a non-aqueous electrolyte. In batteries,

The L i XMV P_〇 _4, a non-aqueous electrolyte secondary battery characterized that you including those having a particle diameter of not more than 1 0 mu m.

 8. The non-aqueous electrolyte secondary battery according to claim 7, wherein i xMv P〇 has a 10% volume cumulative diameter of 1 μm or less.

9. The non-aqueous electrolyte secondary according to claim 特 徴, wherein the ixv P〇 has a surface area of at least 0.5 m ² Z g in comparison with Brunauer's 'Emmet' tailor. battery.

10. The non-aqueous electrolyte secondary battery according to claim 7, wherein the Li _x MPO is Li Fe PO.

 1 1. General formula L i, which allows reversible doping / dedoping of lithium.

(F ev M,-) Ρ Ο (However, the force is in the range of 0.9 ≤ χ ≤ 1.1, y is in the range of 0 <y 1, and M contains 3d transition metal A positive electrode having a positive electrode active material containing the compound represented by the formula (1), a negative electrode having a negative electrode active material capable of reversibly doping with Z, and a non-aqueous electrolyte are provided. In a water electrolyte secondary battery,

The _{L i x (F ev M,} -:,) P_〇, in scan Bae-vector Ritokura is by the main Subaua spectroscopy, isomer shift Toys linear force; 0. 1 mm / sec or more on, 0 The area intensity of the spectrum within the range of 7 mm / sec or less is A, and the isomer shift value is 0.8 mm / sec or more and 1.5 mm / sec. Non-aqueous electrolyte secondary battery characterized in that A / B is less than 0.3, where B is the area intensity of the spectrum in the range of sec or less.

12. The non-aqueous electrolyte secondary battery according to claim 11, wherein the Li is a Li Fe PO ₄ .

1 3. General formula L _x M, PO-, (however, X force; 0 x X 2 range, y is 0.8 ≤ y ≤ 1.2, M is 3 d transition A mixing step of mixing the raw materials for synthesizing the compound represented by the formula (1) to form a precursor;

 A firing step of firing and reacting the precursor obtained in the mixing step,

 A method for producing a positive electrode active material, comprising firing the precursor at a temperature in the range of 400 ° C. or more and 700 ° C. or less in the firing step.

 14. The positive electrode active material according to claim 13, wherein in the firing step, the precursor is fired at a temperature in a range of 400 ° C. or more and 600 ° C. or less. Production method.

15. The method for producing a positive electrode active material according to claim 3, wherein i _x M and .PO are Li Fe PO.